JPH06350171A - Solid-state laser device and integral sphere - Google Patents

Abstract

PURPOSE:To suppress a loss of excited beams within an excited cavity for a solid-state laser by a method wherein a reflector is made as a diffused reflection reflector made of foamed glass and the rear surface is coated with a high reflection material. CONSTITUTION:When foamed glass is used for a reflector, laser beams 10 generated in an exciting lamp 4 are directly received by a laser medium 1 composed of a slave-like YAG crystal, however most of beams except for the beams 10 are received by a foaming glass reflector 6 and make a diffused reflection due to minute air bubbles. A large amount of the received beams 10 are reflected several times and then released, however as transmissivity of, for example, quartz can be deemed as 100% in actuality, a reflection rate becomes almost 100%. However, as beams released onto the reverse surface of the reflector 6 become a loss, silver plating is applied onto the rear surface of the diffused reflection reflector 6 to prevent a transmission of the beams 10 to the rear surface of the reflector to enhance the reflection rate. Accordingly, it is possible to obtain a high reflection rate and effectively oscillate a laser.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state laser device for exciting a solid-state laser medium with light to oscillate a laser and an integrating sphere used in an optical measuring system.

[0002]

2. Description of the Related Art A solid-state laser represented by a YAG laser using Y ₃ Al ₅ O ₁₂ as a solid-state laser medium is small and easy to use. Therefore, in addition to the laser processing field, which has already been used extensively, it has recently become widely used in various fields such as measurement and medicine. Generally, in a solid-state laser device, a column-shaped (rod) -shaped or plate-shaped (slab) -shaped laser medium is excited by a discharge tube such as a krypton flash lamp arranged in parallel with the laser medium to oscillate the laser.

The biggest problems of the solid-state laser are the following two. (1) Increasing oscillation efficiency (2) Eliminating problems caused by heat generation of the laser medium To solve this problem, the following is required. (a) Efficiently injecting the light emitted from the excitation light source into the laser medium (b) The excitation light has a wavelength distribution suitable for laser oscillation One of the measures from the viewpoint of (a) is the excitation light Is to increase the reflectance of the reflector that reflects light. For this purpose, reflectors made of various highly reflective materials have been used conventionally. The most common is a gold-plated reflector of copper or brass. In addition, silver-plated reflectors, ceramic reflectors, and the like are known.

In the slab laser using a plate crystal in the solid-state laser, in order to achieve (a), the crystal heat insulating material must be made of a material that does not absorb light, like the reflector. The laser medium of the slab laser cools a pair of side surfaces of the slab side surfaces that are totally reflected because the laser light propagates in a zigzag shape in order to form a one-dimensional thermal gradient inside the two side surfaces. The structure is such that the materials are in close contact with each other to prevent heat flow. Since this heat insulating material is located in the vicinity of the laser medium, absorption of light not only reduces the efficiency of the laser, but also causes the heat insulating material to generate heat and heat the laser medium. Therefore, the heat insulating material used for the slab laser needs to have a high thermal conductivity or a high reflectance or a high transmittance for the laser light and the excitation light, in addition to having a low thermal conductivity. So as this heat insulating material,
Conventionally, glass, ceramics, etc. have been used.

As another method for improving the oscillation efficiency according to (b), there is a method of converting the wavelength distribution of the pumping light into a distribution suitable for pumping the laser medium. A small part of the emission spectrum of the lamp that is suitable for laser oscillation is a major cause of the low efficiency of the lamp-pumped solid-state laser. Therefore, the idea is to convert the wavelength of the excitation light by using a substance that emits fluorescence having a wavelength suitable for laser oscillation.

In a well-known method, samarium (Sm) or Japanese Patent Laid-Open No. 61-23 is used in a solid-state laser using a laser medium doped with Nd ³⁺ as a laser active material.
There is a method of using glass doped with cerium (Ce) as an excitation light filter, which is disclosed in Japanese Patent No. 374. They absorb light in the ultraviolet region and have a wavelength of λ = 0.6
Fluorescence around μm is emitted. Since Nd ³⁺ has one of the absorption peaks in this wavelength region, it absorbs fluorescence with high efficiency and the oscillation efficiency is improved.

In a similar method, AlGa disclosed by Japanese Patent Application Laid-Open No. 2-123776 of the present invention is disclosed.
There is a method of converting the excitation light wavelength using an As semiconductor.
The band gap of the AlGaAs semiconductor is λ = 810n
Since it corresponds to the photo energy near m, the excitation light on the shorter wavelength side is absorbed, and the light near λ = 810 nm is emitted as fluorescence. Light of this wavelength is most suitable for pumping Nd ³⁺ , and since Nd ³⁺ is pumped by this light, highly efficient oscillation becomes possible.

In both the method using a glass filter doped with Sm or Ce and the method using an AlGaAs semiconductor filter, a part of excess thermal energy is generated in these filters, and the heat load on the laser crystal is reduced. be able to. Therefore, these are effective means for solving the problem (2) caused by the heat generation inside the solid-state laser crystal.

As a method for improving the efficiency of a solid-state laser using Nd ³⁺ as an active material, a book “Solid” by W. Koechner is given.
State Laser Engineering, IIIrd Ed "Spninger-Verlag Publishing (1992) P57, Nd and Cr
Doped with Gd ₃ Sc ₂ Ga ₃ O ₁₂ (Nd, Cr: G
There is a method of using a multi-element doped laser medium such as SGG). In general, the absorption spectrum of Nd ³⁺ doped in a solid-state laser medium exhibits a localized distribution close to a line spectrum, and thus does not match well with the spectral distribution of lamp light. This is a major cause of the low efficiency of Nd: YAG lasers. On the other hand, Cr ³⁺ is 400 to 650 nm
It shows a broad absorption spectrum over the range. So Nd, C
r: GSGG etc. absorbs the excitation light in a wide wavelength range by Cr ^3+, exciting the Nd ³⁺ by a so-called sensitizing effect of transferring energy from the excited state of Cr ³⁺ to an excited state of Nd ^3+. Therefore, since the excitation light in a wide wavelength range is effectively used, the efficiency is improved as compared with the case where Nd ³⁺ is used alone. This method changes the absorption spectrum of the laser medium instead of converting the pumping light wavelength, and can be considered as a kind of method aiming at the above (b).

A method having a slightly different concept from the above method is disclosed in Japanese Patent Publication No. 5-66035. This is N
A multi-element-doped solid laser rod such as d, Cr: GSGG and an Nd: YAG rod are arranged in series, and excitation light is injected from the multi-element-doped solid laser rod side to excite both. In this method, a multi-element-doped solid-state laser medium absorbs light in a wide wavelength range and oscillates, and light passing through this medium excites Nd: YAG to oscillate. Light that has passed through the multi-element-doped solid-state laser medium has a wavelength distribution suitable for Nd: YAG excitation, so that highly efficient laser oscillation is possible as a whole.

The above is related to the prior art for improving the efficiency of the solid-state laser, but in addition to this, there is an integrating sphere as a device related to the reflection of light and similarly required to reduce the loss of light energy. For example, when measuring the energy of light, the area of the light receiving part of the photodetector is usually limited, so if the intensity distribution of the light to be measured is different and the proportion of light that can be received is different, light with the same energy will be detected. Even if there is, different measurement results will be obtained. The integrating sphere is used in such a case, and is devised so that the intensity distribution becomes uniform while the injected light repeats diffuse reflection on the inner surface thereof. As the highly reflective substance on the inner surface of the integrating sphere, M
White paints containing gO or BaSO ₄ as a main component are generally used.

[0012]

[PROBLEMS TO BE SOLVED BY THE INVENTION] Gold-plated reflector
Has a wavelength of 0.8 which greatly contributes to the oscillation of the YAG laser.
High reflectance for light near μm, stains on the plated surface,
An excellent feature that there is little decrease in reflectance due to deterioration
There is. However, the reflectance of the gold-plated surface is 0.6 μm
Since it decreases at the following wavelengths, the Nd: YAG crystal has 0.5-0.5
Large loss for light absorbed in 0.6 μm absorption band
Therefore, there is a limit to the excitation efficiency. Also, Cr, Nd:
GSGG and Cr: BeAl₂O₂(Alexandrite
 ) Cr ³⁺In laser crystals doped with, 0.5 to 0.5.
Since there is a large absorption band in the wavelength range of 6 μm,
A gold-plated reflector is used for a solid-state laser device that uses a laser medium.
Is not suitable.

Further, there is a silver plating reflector as a reflector having a high reflectance in the short wavelength region, but the biggest problem is that silver forms a sulfide and the reflectance is lowered. This problem can be solved by coating the surface of silver with a protective film such as SiO ₂ or by plating the back surface of the glass with silver so that the silver surface does not come into direct contact with the cooling water. However, in a high-power laser, the reflection surface is damaged by the heat generated by the excitation light, and thus it is difficult to use the silver-plated reflector.

Further, in recent years, a reflector using a ceramic having a high reflectance in a short wavelength region has been receiving attention. However, the ceramic reflector is not always sufficient in terms of reflectance. Further, in a reflector using so-called free-cutting ceramics in which ceramic particles are dispersed in a glass matrix, there is a problem that light is transmitted through the ceramic material to reduce the reflectance.

On the other hand, the integrating sphere has the same problem as the laser reflector. That is, although the coating material containing MgO or BaSO ₄ is an extremely excellent material for weak light, the resistance to light is not sufficient when high-power laser light is targeted. The glass that has been conventionally used as a heat insulating material in slab lasers is
It has no absorption for both laser beams. However, there are drawbacks that it is difficult to process and the strength is not sufficient. Ceramics is a relatively suitable material as a heat insulating material for this purpose, but since it absorbs light in the short wavelength region, heating due to this causes a problem. Further, it cannot be said that both glass and ceramics have sufficiently low thermal conductivity as a heat insulating material.

In order to increase the oscillation efficiency of the solid-state laser, S
It has been known that the method of using m or Ce doped glass as an excitation light filter has a low fluorescence emission efficiency, and even if the efficiency of the solid-state laser is improved, it is small. A
Although a method of converting the wavelength of excitation light using an lGaAs semiconductor is promising, the problem is that the refractive index of AlGaAs is extremely high, which is 3 or more. When the refractive index is high, most of the excitation light is reflected, so that the incident light is small, and the light whose wavelength is converted inside is difficult to be emitted to the outside. Further, it is a practical problem that this material is easily oxidized.

A method using a multi-element-doped solid-state laser medium such as Nd, Cr: GSGG is an effective means for improving efficiency, but since extra heat energy is generated inside the crystal,
Reduction of the heat load of the laser medium cannot be expected. Rather GS
Since GG and the like have a lower thermal conductivity than YAG, there is a drawback that the influence of heat generation is significant. Nd, Cr: GSGG
A multi-element-doped solid laser rod and a Nd: YAG rod are arranged in series, and pumping light is injected from the multi-element-doped solid laser rod side to excite the two. That is the problem. Depending on the application, two-wavelength oscillation may be permitted, but if the wavelength range has a width, there are many inconvenient points such that the influence of the chromatic aberration of the lens becomes significant. In addition, in terms of the significant effect of heat, N
This is the same as the case where d, Cr: GSGG or the like is used alone.

A first object of the present invention is to solve the problems of the conventional solid-state laser reflector and to provide a high-efficiency solid-state laser device using a reflector having a high reflectance in the near infrared to ultraviolet region. To do. A second object of the present invention is to solve the problems of the conventional heat insulating material for slab lasers, low thermal conductivity, excellent durability, no light absorption from near infrared to ultraviolet region, and processability. An object of the present invention is to provide a high-efficiency, high-beam-quality solid-state laser device using an excellent heat insulating material.

A third object of the present invention is to solve the problems of the conventional method of converting the wavelength of the pumping light to the optimum one, and to carry out highly efficient pumping light wavelength conversion for practical use. To provide a solid-state laser device. A fourth object of the present invention is to provide an integrating sphere that can withstand strong light such as high power laser light.

[0020]

In order to achieve the above-mentioned first object, a first invention according to claim 1 is an optical resonator including a solid-state laser medium, and pumps the solid-state laser medium. In the solid-state laser device provided with a light source for this purpose and a reflector having a reflecting surface facing the light source and the solid-state laser medium, the reflector is made of foam glass. In order to achieve the same object, the second invention according to claim 2 is the same solid-state laser device, wherein the reflector is a diffuse reflection reflector, and the back surface thereof is covered with a highly reflective material. . Also in that case, the diffuse reflection reflector is preferably made of foam glass.

In order to achieve the above-mentioned second object, a third aspect of the present invention according to claim 4 is a plate-like solid laser medium having a pair of opposed side surfaces which are optically polished surfaces, and a laser medium of this laser medium. In a solid-state laser device including a total reflection mirror and an output mirror that face each other with both end faces sandwiched between them, and a heat insulating material that adheres to a side surface of the medium other than the optically polished surface, the heat insulating material is made of foam glass.

In order to achieve the third object mentioned above,
The fourth aspect of the present invention described in Item 5 is Nd.³⁺Doped
Optical resonator including solid-state laser medium and solid-state laser medium
And a solid-state laser medium for exciting the
With a reflector having a reflective surface opposite the quality
In the laser device, the reflection surface of the light source and reflector
Between the solid laser medium and Cr³⁺From a crystal doped with
It is assumed that a filter that In that case, the crystal
But Y₃Al_FiveO₁₂, Y₃Ga_FiveO₁₂, Y₃Sc ₂Ga
₃O₁₂, Gd₃Ga_FiveO₁₂, Gd₃Sc₂Ga₃O₁₂,
La₃Lu₂Ga ₃O₁₂, KYnF₃, BeAl
₂O_Four, LiSrAlF₆And LiCaAlF ₆Nou
It should be one of them. Or the same third purpose
In order to achieve, a fifth main claim according to claims 7 and 8
The present invention of the sixth and sixth aspects is a solid-state laser device similar to the above.
, The reflective surface of the light source and reflector, and the solid-state laser
Cr between the medium³⁺Doped glass or Ti
³⁺Al doped with₂O₃With a filter consisting of
And

In order to achieve the above-mentioned fourth object, the integrating sphere of the seventh aspect of the present invention described in claim 9 is such that the wall having a spherical inner surface is made of foam glass.

[0024]

The glass foam contains fine closed cells of several hundreds of microns in the glass. For example, when the glass is quartz glass (SiO ₂ ), its specific gravity is 1/10 to 1/2 that of ordinary quartz glass. In addition, this material has a small thermal conductivity of about 1/10 that of quartz and is easy to process.
It is used as a heat insulating material. The present inventors considered that, for example, quartz glass itself is a material having a high transmittance up to the ultraviolet region, but foam glass has a high reflectance due to the existence of numerous solid-gas interfaces inside. This is just like the high reflectance of snow, which is a collection of fine ice.

In the first present invention, this foam glass is used alone. Most of the light generated by the excitation light source is directly incident on the laser medium, and most of the light is incident on the foam glass reflector and is diffusely reflected by the fine bubbles. Most of the incident light is emitted to the outside of the reflector after being reflected several times. Although some diffuse reflection is repeated many times, for example, since the transmittance of quartz can be regarded as 100% in fact, it is eventually emitted outside the reflector. That is, the reflectance is almost 100%. However, since the light emitted to the back surface of the reflector becomes a loss, the foam glass reflector of the first invention requires a certain thickness. Quartz is ideal as the material of the foam glass, but other glass materials such as borosilicate glass may be used as long as they can absorb some light in the short wavelength region. As described above, according to the first aspect of the present invention, since the loss of the excitation light at the reflector is almost eliminated, highly efficient laser oscillation is possible.

In the second aspect of the present invention, the back surface of the diffuse reflection reflector is coated with a highly reflective material such as silver. As described above, the foam glass reflector of the first invention needs a certain thickness in order to prevent the transmission of light to the back surface. Therefore, in the second invention, the back surface of the diffuse reflection reflector is plated with silver to prevent the transmission of light to the back surface of the reflector to increase the reflectance. Therefore, high reflectance can be obtained with a small reflector, and high-efficiency laser oscillation can be achieved. If a diffused glass reflector is used with a foamed glass filter, the reflectance will be higher, but it is also possible to use the free-cutting ceramic reflector described in the section of the prior art. In addition to silver, powders of MgO and BaSO ₄ , powders of white paint used for the inner surface coating of the integrating sphere, highly reflective resins developed as laser reflector materials, and the like can be used as the highly reflective material.

As described above, the biggest problem in using a highly reflective material other than gold as a reflector material for a solid-state laser is that these materials cannot withstand strong excitation light. However, according to the second invention, most of the excitation light is reflected by the diffuse reflection reflector, and the amount of light that actually reaches the highly reflective material outside thereof is very small. That is, the highly reflective material is used to reflect the weak light leaking from the diffuse reflection reflector,
It is not necessary to consider the resistance to light so much. Further, since these highly reflective materials are in close contact with the back surface of the diffuse reflection reflector and the actual reflective surface does not come into contact with cooling water or the like, they can be used for materials such as silver whose surface deterioration is a problem.

In the third aspect of the present invention, foam glass is used as a heat insulating material for a slab laser. Foam glass is as described above
Since it has low thermal conductivity, high reflectance, and excellent workability, it exhibits ideal performance as a heat insulating material for a slab-shaped laser medium. The materials used in the fourth, fifth and sixth aspects of the present invention have been conventionally used as a solid-state laser medium. However, the emission spectra of these are, for example, those of the above-mentioned JP-A-2
Λ = 810n described in Japanese Patent No. 123776.
It has a maximum at a wavelength suitable for excitation of Nd ³⁺ near m. From this, the inventor thought that these materials were rather suitable as materials for wavelength conversion of excitation light. When used as a laser medium, high optical homogeneity is required over the entire crystal, and therefore it is extremely difficult to grow a large crystal that satisfies these requirements. However, if it is premised on the application to a pumping light wavelength conversion filter, such a high-quality crystal is not necessary, and a large crystal used for this purpose can be easily manufactured. Further, a crystal having a low thermal conductivity and a strong thermal lens effect when used as a laser crystal and sufficient performance cannot be obtained can be sufficiently used. For example Ti
Crystals such as Al ₂ O ₃ (Ti: Sapphire) doped with ^3+, which require strong excitation to be used as a laser crystal due to their short fluorescence lifetime, also have short fluorescence lifetime. Means that the transition probability is large and the emission efficiency of fluorescence is high, so that it is rather desirable as a wavelength conversion filter.

These wavelength conversion filters have λ = 400.
It absorbs the excitation light of ˜650 nm and emits the light in the vicinity of λ = 810 nm, which is suitable for the excitation of Nd ³⁺ . Of course, since the light around λ = 810 nm that does not require wavelength conversion is transmitted as it is, the efficiency is improved by the amount of the wavelength-converted excitation light. In the seventh aspect of the present invention, foam glass is used as the diffuse reflection material of the integrating sphere. As described in the first invention, since the foamed glass has a high reflectance and a high proof stress against light, the integrating sphere according to the seventh invention can be used for high-power laser light.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings in which common portions are given the same reference numerals. Figure 1
(a) and (b) show a slab YAG laser of the first invention and one embodiment of the third invention described in claim 4.
In the figure, a laser medium made of a slab-shaped YAG crystal 1 is arranged between a total reflection mirror 2 and an output mirror 3, and an excitation flash lamp 4 is installed so as to face the upper and lower side surfaces thereof. An ultraviolet blocking borosilicate glass filter 5 is interposed between the excitation lamp 4 and the YAG crystal slab 1, and a reflector 6 exists behind the lamp 4. YA
The heat insulating material 7 is in contact with the horizontal side surface of the G crystal slab 1. Water 8 can be caused to flow in the cavity surrounded by the filter 5 and the reflector 6 to cool the excitation lamp 4. The laser light 10 travels in a zigzag through the YAG crystal slab 1. According to the first and third inventions, the reflector 6
The side heat insulating material 7 is made of expanded quartz glass.

Some of the light emitted from the excitation lamp 4 passes through the filter 5 and enters the YAG crystal slab 1 directly, but most of the light follows a complicated path. That is, what is incident on the YAG crystal slab 1 after being diffusely reflected by the expanded quartz glass reflector 6, what is absorbed by the cooling water 8, what leaks to the outside from the cooling water inlet / outlet,
There are various types such as those leaking from the back surface of the reflector 6 and those leaking to the opposite side without being absorbed by the crystals even if they enter the YAG crystal slab 1. It has been found that when a conventional gold-plated reflector is used, the percentage of light absorbed by the reflector is as high as 50%. In this way, most of the excitation light is absorbed by the reflector because it has many opportunities to be reflected by the reflector as described above, and the reflectance of the gold-plated reflector is 90 μm or less for light of 0.6 μm or less. This is due to the decrease to%. On the other hand, in this embodiment, since the reflectance of the foamed silica glass is almost 100% and the absorption by the reflector 6 is extremely small, the proportion of the light absorbed by the YAG crystal slab 1 is increased and the high efficiency laser is obtained. Oscillation is possible.

Further, in this embodiment, since the side surface heat insulating material 7 is also made of foamed quartz, there is almost no absorption in this portion, and more efficient laser oscillation can be achieved. Since expanded quartz has a low thermal conductivity, it has excellent heat insulation performance on the side surface of the slab and high beam quality. FIG. 2 is a second embodiment of the present invention. In this figure, the side view is similar to that of FIG.
Only the cross-sectional view is shown. In this embodiment, a silver plating layer 9 is adhered to the back surface of the foam quartz reflector 6. The reflector 6 is thinner than in the case of FIG. 1, and a part of the light incident on the reflector reaches the back surface.
Since it is reflected by the surface of, the light leakage to the back side of the reflector is eliminated.

FIG. 3 is a different embodiment of the second invention. Since the side view of this embodiment is similar to that of FIG. 1, only a sectional view is shown. In this embodiment, magnesium oxide is provided between the foam quartz reflector 6 and the protective cover 12.
(MgO) powder 11 is filled. Since the reflectance of MgO is extremely high at 95%, it is possible to prevent light from leaking to the back surface of the reflector, like the surface of the silver plating layer 9 shown in FIG.

As can be seen from the embodiments shown in FIGS. 2 and 3.
The reflector according to the second aspect of the present invention is the reflector of the first aspect of the present invention.
Higher efficiency as it has higher reflectance than the reflector 6.
Laser oscillation is achieved. In addition, the foamed quartz reflector 6
Since the thickness of the device can be reduced, the device can be downsized.
It becomes Noh. 4 (a) and 4 (b) show the first and third inventions of the present invention.
Combined with any of the fourth, fifth, and sixth inventions
This is an example. In this example, the borosilicate glass of FIG.
Substituting the wavelength filter 51 instead of the filter 5
There is. The wavelength conversion filter 51 is a flash lamp 41.
Is most suitable for the excitation of YAG in the vicinity of λ = 810 nm
Convert to light. This filter 51 is defined by claim 6 or 8.
Cr described in³⁺Doped with Y₃Al₃O₁₂ (Y
AG), Y₃Ga_FiveO₁₅ (YGG), Y₃Sc₂Ga₂
O₁₂ (YSGG), Gd₃Ga_FiveO₁₂ (GGG), Gd
₃Sc₂Ga ₃O₁₂ (GSGG), La₃Lu₂Ga₃
O₁₂ (LLGG), KYnF₃ (KYF), BeAl₂
O_Four(Alexandrite), LiSrAlF₆(Li
SAF), LiCaAlF₆ (LiCAF), Cr³⁺To
Doped glass or Ti ³⁺Al doped with₂O
₃Use either (sapphire). But these
In order to prevent it from being deteriorated by ultraviolet rays
As a flash lamp 41 for excitation,
A material doped with cerium (Ce) is used. Flashy
Of the light emitted by the lamp 41 near λ = 810 nm
Light passes through the wavelength conversion filter 51 and directly passes through the YAG crystal.
1, but most of the light at λ = 400-650 nm
Is absorbed by the wavelength conversion filter 51 and has λ = 810 nm
Converted to near light, this converted light is absorbed by YAG crystal 1.
To be done. That is, most of the excitation light is used to excite YAG.
It will be converted into the most suitable λ = 810 nm light.
Therefore, laser oscillation with extremely high efficiency becomes possible. Further
Most of the light energy that does not contribute to laser oscillation is wavelength converted
Since it is converted into heat energy in the filter 51, YA
The heat load on the G crystal 1 is reduced, and the crystal of the thermal lens effect etc.
The effect caused by heat generation is reduced, and the beam of oscillation laser light is
Quality is improved.

FIG. 5 shows an embodiment of the rod type YAG laser of the fourth, fifth and sixth aspects of the present invention. That is, the rod-shaped Nd: YAG crystal 21 is the laser medium. In this embodiment, the reflector 22 using ceramics as a material is used. This reflector 22
Accommodates a tubular wavelength conversion filter 52 surrounding the YAG crystal rod 21 and a borosilicate glass flow tube 23 surrounding the flash lamp 2. The flow tube 23 serves as a passage for cooling water flowing from the inlet 24 to the outlet 25, and the cooling water cools the lamp 2. Further, the space between the YAG crystal rod 21 and the filter 52 has an inlet 26
The cooling water flows from the outlet to the outlet 27, and the cooling water cools the YAG crystal rod 21. Space between filter 52 and flow tube 23 and reflector 22
Also, the cooling water is filled. The material of the filter 52 is shown in FIG.
Like the filter 51 of Cr: YAG, Cr: YGG,
Cr: YSGS, Cr: GGG, Cr: GSGG, C
r: LLGG, Cr: KYF, Cr: LiSAF, C
r: LiCAF, Cr-doped alexandrite, Cr
It is either doped glass or Ti-doped sapphire.

FIG. 6 shows an integrating sphere used for measuring the power of laser light in the seventh embodiment of the present invention. This integrating sphere is
It comprises a wall 31 having a spherical space 32 therein, which wall is made of expanded quartz according to the invention. Wall 31
The laser light 10 entering the space 32 through the entrance 33 provided on one side is diffusely reflected by the inner surface of the wall body 31. The light repeats reflection, leaks again to the outside from the entrance 33, and except for a part of the light that passes through the foamed quartz, reaches the detector 35 fitted in the exit 34 and the power is measured. Since the laser light 10 is diffusely reflected inside the space 32 and a uniform intensity distribution is obtained, it is possible to measure the power without being affected by the intensity distribution of the laser light before the incidence on the integrating sphere. In this embodiment, since the reflecting surface is made of expanded silica, it has a high resistance to laser light and can be applied to a high-power laser without any problem.

[0037]

According to the first and second aspects of the present invention, the solid-state laser is provided by using the foam glass for the reflector or by providing the highly reflective material layer for reflecting the light emitted to the back side of the diffuse reflection filter. It is possible to suppress the loss of pumping light in the pumping cavity. As a result, it has become possible to significantly increase the oscillation efficiency of the solid-state laser. According to the third aspect of the present invention, by using the foam glass as the heat insulating material, the side heat insulation performance of the slab laser can be improved and the beam quality can be improved.

According to the fourth, fifth and sixth inventions, Nd
Most of the excitation light of a solid-state laser using a ^{3 +} -doped laser medium is converted into the most suitable light for excitation by using a wavelength conversion filter made of a substance doped with Cr or Ti trivalent ions. You can As a result, extremely high efficiency laser oscillation is possible. Furthermore, most of the light energy that does not contribute to laser oscillation is converted into heat energy in the wavelength conversion filter, so the heat load on the laser crystal is reduced, and the effects due to heat generation of the crystal such as the thermal lens effect are reduced. It was possible to improve the beam quality of the oscillated laser light.

According to the seventh aspect of the present invention, it is possible to provide an integrating sphere applicable to high-power laser light by forming a wall body having a spherical inner surface from foam glass.

[Brief description of drawings]

1A and 1B are configuration diagrams of a solid-state laser device according to an embodiment of the first and third aspects of the present invention, in which FIG. 1A is a side sectional view of the device, and FIG.
(a) AA line sectional view taken on the line in FIG.

FIG. 2 is a sectional view showing the configuration of a solid-state laser device according to an embodiment of the second invention.

FIG. 3 is a sectional view showing a configuration of a solid-state laser device according to another embodiment of the second invention.

FIG. 4 is a configuration diagram of a solid-state laser device according to an embodiment of the fourth, fifth and sixth aspects of the present invention, in which (a) is a side sectional view of the device,
(b) is a sectional view taken along the line BB in (a).

5A and 5B are configuration diagrams of solid-state laser devices according to different embodiments of the fourth, fifth, and sixth aspects of the present invention, in which FIG. 5A is a side sectional view of the device, and FIG. 5B is CC in FIG. Sectional view taken along the line

FIG. 6 is a sectional view showing the structure of an integrating sphere according to an example of the seventh invention.

[Explanation of symbols]

 1 YAG Crystal Slab 2 Total Reflection Mirror 3 Output Mirror 4, 41 Excitation Lamp 5 Filter 51, 52 Wavelength Conversion Filter 6 Foam Quartz Reflector 7 Side Thermal Insulation 9 Silver Plated Layer 10 Laser Light 11 MgO Powder 21 YAG Crystal Rod 22 Ceramics Reflector 31 Walls 32 Spherical Space 33 Inlet 34 Outlet 35 Detector

Claims (9)

[Claims] 1. A reflector comprising: an optical resonator including a solid-state laser medium; a light source for exciting the solid-state laser medium; and a reflector having a reflecting surface facing the light source and the solid-state laser medium. A solid-state laser device comprising a foam glass. 2. A reflector comprising an optical resonator including a solid-state laser medium, a light source for exciting the solid-state laser medium, and a reflector having a reflecting surface facing the light source and the solid-state laser medium. A solid-state laser device which is a diffuse reflection reflector, the back surface of which is coated with a highly reflective material. 3. The solid-state laser device according to claim 2, wherein the diffuse reflection reflector is made of foam glass. 4. A plate-shaped solid-state laser medium having a pair of opposed side faces which are optically polished faces, a total reflection mirror and an output mirror which face each other with both end faces of the laser medium interposed therebetween, and other than the optically polished faces of the medium. And a heat insulating material that adheres to the side surface of the solid laser device. 5. An optical resonator including a solid laser medium doped with trivalent neodymium ions, a light source for exciting the solid laser medium, and a reflector having a reflecting surface facing the light source and the solid laser medium. A solid-state laser device comprising a light source, a reflecting surface of a reflector, and a solid-state laser medium, and a filter made of a crystal doped with trivalent chromium ions. 6. The crystal is Y ₃ Al ₅ O ₁₂ , Y ₃ Ga.
₅ O ₁₂ , Y ₃ Sc ₂ Ga ₃ O ₁₂ , Gd ₃ Ga ₅ O ₁₂ , G
_{d 3 Sc 2 Ga 3 O 12} , La 3 Lu 2 Ga 3 O 12, KY
nF ₃ , BeAl ₂ O ₄ , LiSrAlF ₆ and Li
The solid-state laser device according to claim 5, which is one of CaAlF ₆ . 7. An optical resonator including a solid-state laser medium doped with trivalent neodymium ions, a light source for exciting the solid-state laser medium, and a reflector having a reflecting surface facing the light source and the solid-state laser medium. A solid-state laser device comprising a filter made of glass doped with trivalent chromium ions between the light source and the reflecting surface of the reflector and the solid-state laser medium. 8. An optical resonator including a solid-state laser medium doped with trivalent neodymium ions, a light source for exciting the solid-state laser medium, and a reflector having a reflecting surface facing the light source and the solid-state laser medium. A solid-state laser device comprising: a light source, a reflecting surface of a reflector, and a solid-state laser medium, and a filter made of Al ₂ O ₃ doped with trivalent titanium ions. 9. An integrating sphere characterized in that the wall having a spherical inner surface is made of foam glass.